He made a few points that I wanted to highlight for SEOs:
Do Not Wait Out Penalties
Google said not to wait out penalties because they can take a long time to be reversed. Instead, submit a reconsideration request to help expedite it. John said, "- If you're serious about your site's standing in our search results, then I'd strongly advise not to try to wait the penalty out. These are generally not issues that expire after a few days, they can affect your site's standing for quite some time."
Remove All Paid Links Going Back As Far As You Paid Links
Google said that if you have been paying for links for two years, go back two years and remove those paid links. If it is five year, go back five years. Google wants to see a serious attempt to remove all the paid links you acquired over the years.
John said, "Regarding the age of the unnatural links, I'd work to have them all removed, regardless of the age. For instance, in the general case where a site has been buying links for 2 years, it would be a good idea to go back that far."
Getting A Notification Now Doesn't Mean It Is A New Penalty
Google stepped up their notifications, so if you get a notification today, it doesn't mean it is a new penalty. Google is sending notifications out for old penalties. John explained, "while we have just recently started sending out these messages, they may apply to issues that were already known (and affecting your site's standing in our search results) for a while."
John added a few more points we covered here a few times but feel free to check out the Google Webmaster Help thread.
Forum discussion at Google Webmaster Help.
Image credit to ShutterStock for paid links.